Advanced Materials Research Vols. 834-836

Abstract: The cracking failure phenomenon of kitchen knife made by 5Cr15MoV steel was analyzed by chemical composition detection, hardness measurement, metallographic examination and SEM analysis methods. The results showed that the crack was mainly due to the organizational stress caused by carbide segregation in steel. Overhigh hardness and substandard chemical composition were the secondary cause of cracking.

Abstract: The quaternary TixZr_1-xMnFe gettering alloys (x =0, 0.1, 0.2, 0.3 and 0.4) were synthesized successfully by arc melting and their phase structures along with microstructures had been investigated by optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM). It showed that the addition of Ti did not change the phase structure of ZrMnFe of C14 laves phase. XRD results showed that Ti successfully replaced part of the Zr and the decrease of interplanar spacing had a linear relationship with the increase of Ti content. The success of this trial preparation provides reference for nuclear industry gettering materials.

Abstract: Experimental investigations of fatigue cracking behavior of LC9 aluminum alloy (AA LC9) subjected to elevated temperature were conducted with scanning electron microscope (SEM). Results indicate elevated temperature is important for the fatigue crack growth of AA LC9. Based on small crack growth, crack growth rate for AA LC9 is characterized.

Abstract: Effects of minor silver addition on microstructure, mechanical properties and corrosion resistances of Al-8Zn-1.Cu-1.3Mg-0.1Zr alloys were investigated using optical microscope (OM), scanning electron microscopy (SEM), mechanical properties and corrosion testing. The results show that minor silver addition decreases the recrystallization and corrosion resistance of the t77-tempered alloys.Tensile strength of the based alloy was increased by the 0.1 wt% silver addition.

Abstract: The results of preliminary experimental researches of possibility of metallurgical processing of ores of Actually Kachkanarsky deposit are presented in the work.

Abstract: Pitting resistance of super martensitic stainless steel 00Cr13Ni5Mo2 made in China has been investigated by employing electrochemical technology and chemical immersion methods. The results showed that pitting potential of super martensitic stainless steel decreased with the increasing of NaCl concentration and temperature, respectively. And corrosion rate of super martensitic stainless steel increased with the increasing of temperature. Furthermore, compared to super martensitic stainless steel made in Japan, the domestic one was better in terms of pitting potential, pitting corrosion rate and the density of the pits, but worse in terms of the depth of the pits.

Abstract: To enhance effective use of resources, we use magnetic separation method on the experiment study of a refractory oolitic hematite ore. Research showed that: the grade of raw ore (TFe) was 47.44%, and magnetic iron grade (MFe) was 28.59%. Through magnetic separation experiment, three-step magnetic separation process was chosen. The magnetic field intensity (MFI) of three magnetic separation processes was 1200Oe800Oe400Oe, respectively. After first magnetic separation, the preliminary concentrates was reground to fineness of 87% (-500 mesh). Under the optimal experiment conditions, an iron ore concentrate with grade of 61.11% and a good recovery of 44.35% was obtained.

Abstract: Steel slag is hydraulic cementing material, which is mainly applicable approach to the production of cement, admixture of high performance concrete, road engineering. But as a result of hydration expansion of the free calcium oxide and free magnesium oxide and dicalcium silicate morphological changes which is contained in slag cause poor stability of steel slag used in engineering, the steel slag utilization is very low. Therefore, the key technology of steel slag treatment process is to improve the stability of steel slag. Steel slag is alkaline slag, with lower temperature, the viscosity increases sharply, the liquidity variation, it is one of the important factors affect the steel slag processing, According to the need for different liquidity of steel slag to choose the corresponding steel slag treatment technology. Tank-type hot disintegrating, Rotary cylinder technology processing available to small particle size, good steel slag separation, active promotion of slags, conducive to the comprehensive utilization of steel slag.

Abstract: When disconnecting switches were operated,Very Fast Transient Overvoltage (VFTO) did great harm to power systems and their equipments in Gas Insulated Substations (GIS). Although VFTO can be suppressed by a few of known methods, there were some problems. Low voltage simulation tests show that putting ferrite rings around a disconnecting generatrix can damp traveling wave propagation and suppress VFTO in GIS. This method is economic and practical. We had analyzed ferrite characteristics of suppressing VFTO and got hold of ways of calculating ferrite size in GIS. Investigation shows that ferrite characteristics and sizes have a great effect on suppressing VFTO.

Abstract: The structure and mechanical property changes of Cr34Ni45 ethylene cracking furnace tube serviced for different time (as-cast, 1.5 years and 6 years) are systematically investigated by using SEM, EMPA, XRD and mechanics performance test methods. The microstructure of the as-cast alloy consists of austenitic matrix, NbC and M₇C₃ primary carbides. Eutectic M₇C₃ transform into M₂₃C₆, and the NbC transform into Nb₃Ni₂Si which is so-called η-phase during service, accompany with precipitation of secondary M₂₃C₆. Furthermore, comparing to original uniform microstructure distribution, there are three zones including oxidation layer, carbides depletion zone and carbides-rich zone at the subsurface region of the inner-wall of Cr35Ni45 tubes after long time service. Oxidation behaviors at high temperature consist of external oxidation of chromium and internal oxidation of silicon. The carburizing behavior of Cr35Ni45 tube is mainly caused by the coking on the surface of inner-wall, but carburization of the serviced tubes are both at lesser-degree because of the auto-remediation of outer oxidation layer. High temperature service heavily reduced mechanical performance of the tubes, and fracture mode transform from a mixed mode to a brittle one during service.